It is known that there generally exist two categories of flight plans on an aircraft, namely:                an active flight plan which represents the current flight plan which is followed by the aircraft. This current flight plan is in particular taken into account by a flight management system, of FMS type, which assists the aircraft's pilots with flight management and which uses this current flight plan to perform long-term guidance of the aircraft, both in the vertical plane and in the lateral plane. Of course, a single flight plan is active at any one time on the aircraft; and        secondary flight plans which make it possible in particular to calculate and compare predictions and to anticipate changes of trajectory (for example a change of runway, a diversion, etc.) and which are intended to be able to replace the active flight plan.        
A secondary flight plan that might replace an active flight plan can be created during the phase for preparing the flight on the ground. In this case, the pilot merely has to replace the active flight plan with the secondary flight plan, during a flight, in the event of a change of situation so as to then allow the aircraft to follow this now active secondary flight plan. Nevertheless, such ground preparation is not systematic. So, when a secondary flight plan has not been created in advance, its creation during a flight may become irksome. For this purpose, an operator, in particular the pilot, can create this secondary flight plan from scratch, or make a copy of the active flight plan and then carry out the modifications manually. Accordingly, the operator must in particular inquire about the associated procedures and consult the various maps at his disposal, this creating a significant workload.
The standard creation of a secondary flight plan in this way is therefore not very well suited to a flight, during which the pilot must simultaneously manage other tasks such as aircraft guidance, communication, systems management, etc. To these difficulties may be added a context of stress, since the creation of a secondary flight plan is sometimes done in an emergency situation.
It is known that on certain aircraft, there exist secondary flight plans prepared in advance. Generally, these secondary flight plans exhibit a particular caption. These captions are generic and do not convey the purpose sought when these secondary flight plans were created. The pilot is therefore forced to store the modifications which have been made to create these secondary flight plans, thus creating an additional workload and possibly leading to confusion. So, this standard solution existing on certain aircraft is not completely satisfactory.